A magnified image of real object is to be obtained on large screen 1 m from it. This can be achieved by

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using a convex mirror of focal length less than 0.25 m

using a convex lens of focal length less than 0.25m

using a concave lens of focal length less than 0.25 m

using a concave mirror of focal length less than 0.25 m

answer is B, C.

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Detailed Solution

Formation of real image for real object is possible for concave mirror and convex lens
Considering a concave mirror
object distance =u
Image distance=u+1
Using mirror equation
$\frac{1}{- u} + \frac{1}{- (u + 1)} = \frac{1}{f} u^{2} + (2 f + 1) u + f = 0$

To have real solutions
We get $1 + f^{2} > 0$
So for a cncave mirror there is similarly for convex lens,
The lens is placed in between the object and the screen.
Object distance=u
Image distance =1-u
On using the lens formula and applying the condition to have real solutions
We get $4 f \leq 1,$ so for convex lens the focal length must be less than 0.25 m